1. Field of the Invention
The present invention relates to a column oven for adjusting the temperature of an analytical column of a liquid chromatograph, and a liquid chromatograph using the column oven, and more particularly, to improvement of a temperature control method of the column oven.
2. Description of the Related Art
A liquid chromatograph includes an analytical column for separating a sample into components, and the separation performance of this analytical column greatly affects the analysis result. The separation performance of the analytical column is highly dependent on temperature, and there is a problem that if the temperature of the analytical column changes during an analysis, the reproducibility of the analysis result is impaired. Thus, the analytical column is placed inside a column oven, and the temperature inside the column oven is controlled to maintain a specific temperature (for example, see JP 3539093 B1).
A temperature sensor for detecting the inside temperature is provided to the column oven, and a heating device or a cooling device provided inside the column oven is controlled in such a way that the temperature detected by the temperature sensor is at a temperature set by an analyst. Controlling of the heating device and the cooling device is performed based on the inside temperature of the column oven, and, also, on the ambient temperature of the column oven (room temperature).
If the set temperature set by the analyst is much higher than the room temperature, the temperature inside the column oven is controlled by high output of the heating device, and if the set temperature is much lower than the room temperature, the temperature inside the column oven is controlled by high output of the cooling device. Moreover, if the set temperature is close to the room temperature, the temperature inside the column oven is controlled by turning on or off the heating device or the cooling device. In this manner, controlling of turning on or off, or controlling of the level of output is performed with respect to the heating device and the cooling device according to the relationship between the set temperature and the room temperature.
However, if the ambient temperature of the column oven changes during an analysis, the temperature inside the column oven may change and the stability may be impaired due to the relationship between the set temperature and the ambient temperature of the column oven being changed and the on/off of the heating device and the cooling device being suddenly switched or the output thereof being suddenly changed.